Surface finishes for high density interconnect architectures

ABSTRACT

An electroless nickel, electroless palladium, electroless tin stack and associated methods are shown. An example method to form a solder bump may include forming a layer of a second material over a first material at a base of a trench in a solder resist layer. The first material includes nickel and the second material includes palladium. The method further includes depositing a third material that includes tin on the second material using an electroless deposition process, and forming a solder bump out of the third material using a reflow and deflux process.

BACKGROUND

Traditional stencil-based technologies for fine electrolytic pitchbumping (e.g., Micro-ball bumping or Solder Paste Printing) are reachingscaling limits as pitches become finer in semiconductor packaging. Forhigh bandwidth connectivity packaging, bumping is needed for varyingpitch and solder resist opening (SRO) layer sizes, and the traditionalstencil methods do not work for these types of technologies. Further,electrolytic plating can be used to overcome some of the deficiencies ofstencil-based technologies, but is much more costly (e.g., use of goldand many complex process steps) and has several limitations, includingdry film resist (DFR) compatibility with bump plating bath, stripping ofthe DFR and seed layer without damaging the bump and the DFR adhesion tothe seed layer at finer pitches. Traditional technologies may use goldduring the process of forming a conductive bump. Thus, improved methodsand devices are desirable to address issues including, but not limitedto, reduction in manufacture costs and variable solder bump pitch.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D are a cross section of formation of a solder bump inaccordance with some embodiments of the disclosure.

FIGS. 2A-2D are a cross section of formation of a solder bump inaccordance with some embodiments of the disclosure.

FIGS. 3A-3D are a cross section of formation of a solder bump inaccordance with some embodiments of the disclosure.

FIG. 4 is a cross section of a semiconductor package having varyingpitch solder bumps in accordance with some embodiments of thedisclosure.

FIG. 5 is a flow diagram of an example method of forming a solder bumpin accordance with some embodiments of the disclosure.

FIG. 6 is a flow diagram of an example method of forming multiple solderbumps in accordance with some embodiments of the disclosure.

DESCRIPTION OF EMBODIMENTS

The following description and the drawings sufficiently illustratespecific embodiments to enable those skilled in the art to practicethem. Other embodiments may incorporate structural, logical, electrical,process, and other changes. Portions and features of some embodimentsmay be included in, or substituted for, those of other embodiments.Embodiments set forth in the claims encompass all available equivalentsof those claims.

Although the present disclosure uses elements of semiconductor chippackages, and their method of manufacture as an example, the disclosureis not so limited. Examples of the present disclosure may be used in anytechnology where formation of a solder bump in a solder resist layer iscontrolled.

FIGS. 1A-1D show a cross-section schematic view of formation of a solderbump 121 using an electroless nickel or nickel alloy/palladium/tin ortin alloy (ENEPET) stack in accordance with embodiments of thedisclosure. The package 100, package 101, package 102, and package 103of FIGS. 1A-1D, respectively, may include some of the samematerials/layers/components. Those materials/layers/components that arecommon among all or a subset of the package 100, package 101, package102, and package 103 of FIGS. 1A-1D use common reference numbers. In theinterests of brevity and clarity, description of the formation of thesecommon layers/materials/components will not be repeated for each figure.

Turning now to FIG. 1A, the package 101 may include a SR layer 104having an electrode 106 and a trench 108 that extends vertically to theelectrode 106. The SR layer 104 may include a solder resist (SR)material, such as an epoxy or plastic-organic material. The electrode106 may include copper, a copper alloy, or another conductive material.The trench 108 may be formed by etching a trench in the SR layer 104. Insome examples, the sidewalls of the trench 108 may be angled outwardfrom a horizontal center of the trench 108. In other examples, thesidewalk of the trench 108 may be perpendicular to a top surface of theSR layer 104. The process of forming the solder bump 121 depicted inFIG. 1D may include forming a layer of a first material 110 at the baseof the trench 108. The first material 110 may contact the electrode 106at the base of the trench 108 and the sidewalls of the SR layer 104within the trench 108. The first material 110 may include nickel or anickel alloy such as nickel-phosphorous (Ni—P). Other materials may beused that exhibit conductivity and diffusion barrier properties similarto nickel or nickel alloys, such as cobalt-phosphorous oriron-phosphorous. The deposition of the first material 110 may be via anelectroless deposition process (e.g., an auto-catalytic reaction withoutuse of an electrical field).

As depicted in the package 101 of FIG. 1B, the process of forming thesolder bump 121 depicted in FIG. 1D may further include forming a layerof a second material 112 over the first material HO at the base of thetrench 108. The second material 112 may contact the first material 110at the base of the trench 108 and the sidewalls of the SR layer 104within the trench 108. The second material 112 may include palladium(Pd). The deposition of the second material 112 may be via anelectroless deposition process.

As depicted in the package 102 of FIG. 1C, the process of forming thesolder bump 121 depicted in FIG. 1D may further include depositing athird material 120 over the second material 112 in the trench 108. Thethird material 120 may fill the trench 108 and extend above a topsurface of the SR layer 104. While FIG. 1C depicts the shape of thethird material 120 above the SR layer 104 as being rectangular, one withskill of the art would appreciate that the shape could be other thanrectangular, such as trapezoidal with a greater width at the surface ofthe SR layer 104 than at a top portion. The third material 120 maycontact the second material 112 at the base of the trench 108 and thesidewalls of the SR layer 104 within the trench 108. The third material120 may include tin (Sn) or a tin alloy (e.g., Sn—Cu, Sn—Ag, Sn—Bi,etc.). The deposition of the third material 120 be via an electrolessdeposition process that efficiently deposits the third material 120 ontothe second material 112.

As depicted in the package 103 of FIG. 1D, the process of forming thesolder bump 121 may further include performing a solder reflow anddeflux process on the third material 120 of FIG. 1C. The solder reflowand deflux process may adhere the solder bump 121 to the second material112, the second material 112 to the first material 110 and the firstmaterial 110 to the electrode 106. The solder reflow and deflux processmay also provide the solder bump 121 having a rounded shape above thesurface of the SR layer 104 for connecting to the die. The roundedsurface may have a circular or elliptical shape. The rounded shape mayreduce the likelihood of shorting adjacent contacts together.

The solder bump 121 could then be used with a soldering process to forma solder joint with a die or other electrical component. In someexamples, the solder bump 121 could form an oxide layer. In such cases,the soldering process may include an oxide removal and preferentialsurface wetting. By using the ENEPET stack to form the solder bump 121,cost and time may be reduced as compared with traditional stencil andelectrolytic technologies. In addition, the ENEPET may be used togenerate solder bump 121 on a single SR layer 104 that have differentpitches. In some examples, the solder bump 121 pitches may be less than25 μm, such as 20 μm.

FIGS. 2A-2D show a cross-section schematic view of formation of a solderbump 221 using an ENEPET stack in accordance with embodiments of thedisclosure. The formation process depicted in FIGS. 2A-21) differs fromthe formation process depicted in FIGS. 1A-1D based on when thesidewalls of the SR layer 204 are etched down e.g., after deposition ofthe third material 220) versus when the sidewalls of the SR layer 104are etched down (e.g., prior to deposition of the first material 110).The package 200, package 201, package 202, and package 203 of FIGS.2A-2D, respectively, may include some of the samematerials/layers/components. Those materials/layers/components that arecommon among all or a subset of the package 200, package 201, package202, and package 203 of FIGS. 2A-2D use common reference numbers. In theinterests of brevity and clarity, description of the formation of thesecommon layers/materials/components will not be repeated for each figure.

Turning now to FIG. 2A, the package 201 may include a SR layer 204having an electrode 206 and a trench 208 that extends vertically to theelectrode 206. The SR layer 204 may include a SR material, such as anepoxy or plastic-organic material. The electrode 206 may include copper,or another conductive material. The trench 208 may be formed by etchinga trench in the SR layer 204. In some examples, the sidewalls of thetrench 208 may be angled outward from a horizontal center of the trench208. In other examples, the sidewalk of the trench 208 may beperpendicular to a top surface of the SR layer 204. The process offorming the solder bump 221 depicted in FIG. 2D may include forming alayer of a first material 210 at the base of the trench 208, and thenforming a layer of a second material 212 over the first material 210.The first material 210 may contact the electrode 206 at the base of thetrench 208 and the sidewalls of the SR layer 204 within the trench 208,and the second material 212 may contact the first material 210 at thebase of the trench 208 and the sidewalls of the SR layer 204 within thetrench 208. The first material 210 may include nickel or a nickel alloy,such as nickel-phosphorous (Ni—P) and the second material 212 mayinclude palladium. For the first material 210, other materials may beused that exhibit conductivity and diffusion barrier properties similarto nickel or nickel alloys, such as cobalt-phosphorous oriron-phosphorous. The deposition of the first material 210 and thesecond material 212 may each be via an electroless deposition process(e.g., an auto-catalytic reaction without use of an electrical field).

As depicted in the package 201 of FIG. 2B, the process of forming thesolder bump 221 depicted in FIG. 2D may further include depositing athird material 220 over the second material 212 in the trench 208. Thethird material 220 may extend up to a top surface of the SR layer 204.The third material 220 may contact the second material 212 at the baseof the trench 208 and the sidewalls of the SR layer 204 within thetrench 208. The third material 220 may include tin (Sn) or an alloy oftin (e.g., Sn—Cu, Sn—Ag, Sn—Bi, etc.). The deposition of the thirdmaterial 220 be via an electroless deposition process that efficientlydeposits the third material 220 onto the second material 212.

As depicted in the package 202 of FIG. 2C, the process of forming thesolder bump 221 depicted in FIG. 2D may further include etching the SRlayer 204 to remove a top portion of the SR layer 204. The thirdmaterial 220 may remain in place such that a portion of the thirdmaterial 220 is extends above the SR layer 204. The sides of the thirdmaterial 220 may extend in an outward direction such that a width of thethird material 220 at a top end is greater than a width of the thirdmaterial 220 at a portion adjacent to the etched surface of the SR layer204.

As depicted in the package 203 of FIG. 2D, the process of forming thesolder bump 221 may further include performing a solder reflow anddeflux process on the third material 220 of FIGS. 2B and 2C. The solderreflow and deflux process may adhere the solder bump 221 to the secondmaterial 212, the second material 212 to the first material 210 and thefirst material 210 to the electrode 206. The solder reflow and defluxprocess may also provide the solder bump 221 having a rounded shapeabove the surface of the SR layer 204 for connecting to another die. Insome examples, the solder bump 221 may have a circular or ellipticalshape. The rounded shape may reduce the likelihood of shorting adjacentcontacts together.

The solder bump 221 could then be used with a soldering process to forma solder joint with a die or other electrical component. In someexamples, the solder bump 221 could form an oxide layer. In such cases,the soldering process may include an oxide removal and preferentialsurface wetting. By using the ENEPET stack to form the solder bump 221,cost and time may be reduced as compared with traditional stencil andelectrolytic technologies. In addition, the ENEPET may be used togenerate solder bump 221 on a single SR layer 204 that have differentpitches. In some examples, the solder bump 221 pitches may be less than25 μm, such as 20 μm.

FIGS. 3A-3D show a cross-section schematic view of formation of a solderbump 321 using an ENEPET stack in accordance with embodiments of thedisclosure. The formation process depicted in FIGS. 3A-3D differs fromthe formation process depicted in FIGS. 1A-1D by including deposition ofthe first material 310 and the second material 312 on the sidewalls ofthe trench 308, in addition to deposition on at the base of the trench308. The package 300, package 301, package 302, and package 303 of FIGS.3A-3D, respectively, may include some of the samematerials/layers/components. Those materials/layers/components that arecommon among all or a subset of the package 300, package 301, package302, and package 303 of FIGS. 3A-3D use common reference numbers. In theinterests of brevity and clarity, description of the formation of thesecommon layers/materials/components will not be repeated for each figure.

Turning now to FIG. 3A, the package 301 may include a SR layer 304having an electrode 306 and a trench 308 that extends vertically to theelectrode 306. The SR layer 304 may include a SR material, such as anepoxy or plastic-organic material. The electrode 306 may include copper,or another conductive material. The trench 308 may be formed by etchinga trench in the SR layer 304. In some examples, the sidewalls of thetrench 308 may be angled outward from a horizontal center of the trench308. In other examples, the sidewalls of the trench 308 may beperpendicular to a top surface of the SR layer 304. The process offorming the solder bump 321 depicted in FIG. 3D may include forming alayer of a first material 310 along the base and the sidewalls of thetrench 308. The first material 310 may extend up the entire sidewall ofthe trench 308 to a top surface of the SR layer 304. The first material310 may contact the electrode 306 at the base of the trench 308 and thesidewalls of the SR layer 304 within the trench 308. The first material310 may include nickel or a nickel alloy, such as nickel-phosphorous(Ni—P). Other materials may be used that exhibit conductivity anddiffusion barrier properties similar to nickel or nickel alloys, such ascobalt-phosphorous or iron-phosphorous. The deposition of the firstmaterial 310 be via an electroless deposition process.

As depicted in the package 301 of FIG. 3B, the process of forming thesolder bump 321 depicted in FIG. 3D may further include forming a layerof a second material 312 over the first material 310 along the base andsidewalls of the trench 308. The second material 312 may contact thefirst material 310 along the base and sidewalls of the trench 308. Thesecond material 312 may include palladium (Pd). In some examples, thesecond material 312 may not include nickel (Ni). The deposition of thesecond material 312 be via an electroless deposition process.

As depicted in the package 302 of FIG. 3C, the process of forming thesolder bump 321 depicted in FIG. 3D may further include depositing athird material 320 over the second material 312 in the base of thetrench 308. The third material 320 may extend above a top surface of theSR layer 304. While FIG. 3C depicts the shape of the third material 320above the SR layer 304 as being rectangular, one skilled in the artwould appreciate that the shape could be other than rectangular, such astrapezoidal with a greater width at the surface of the SR layer 304 thanat a top portion. The third material 320 may contact the second material312 along the base and sidewalls of the trench 308. The third material320 may include tin (Sn) or an alloy of tin (e.g., Sn—Cu, Sn—Ag, Sn—Bi,etc.). The deposition of the third material 320 be via an electrolessdeposition process that efficiently deposits the third material 320 ontothe second material 312.

As depicted in the package 303 of FIG. 3D, the process of forming thesolder bump 321 may further include performing a solder reflow anddeflux process on the third material 320 of FIG. 3C. The solder reflowand deflux process may adhere the solder bump 321 to the second material312, the second material 312 to the first material 310 and the firstmaterial 310 to the electrode 306. The solder reflow and deflux processmay also provide the solder bump 321 having a rounded shape above thesurface of the SR layer 304 for connecting to the die. The rounded shapemay reduce the likelihood of shorting adjacent contacts together. Thesolder bump 321 may have a circular or elliptical shape.

The solder bump 321 could then be used with a soldering process to forma solder joint with a die or other electrical component. In someexamples, the solder bump 321 could form an oxide layer. In such cases,the soldering process may include an oxide removal and preferentialsurface wetting. By using the ENEPET stack to form the solder bump 321,cost and time may be reduced as compared with traditional stencil andelectrolytic technologies. In addition, the ENEPET may be used togenerate solder bump 321 on a single SR layer 304 that have differentpitches. In some examples, the solder bump 321 pitches may be less than25 μm, such as 20 μm.

FIG. 4 shows a cross-section schematic view of an apparatus 400 thatincludes a package 410 having a first ENEPET stack 420, a second ENEPETstack 430, a third ENEPET stack 440, and a fourth ENEPET stack 450 inaccordance with embodiments of the disclosure. The die 410 may includethree primary layers: a SR layer 412, a first Ajinimoto build-up film(ABF) film 414, and a second ABF film 416.

The first ENEPET stack 420, second ENEPET stack 430, third ENEPET stack440, and fourth ENEPET stack 450 may each be formed in the SR layer 412.The first ENEPET stack 420 may include a tin or a suitable alloy of “Sn”material 422, a palladium layer 424, and a nickel or nickel alloy layer426. The second ENEPET stack 430 may include a tin or a suitable alloyof “Sn” material 432, a palladium layer 434, and a nickel or nickelalloy layer 436. The third ENEPET stack 440 may include a tin or asuitable alloy of “Sn” material 442, a palladium layer 444, and a nickelor nickel alloy layer 446. The fourth ENEPET stack 450 may include a tinor a suitable alloy of “Sn” material 452, a palladium layer 454, and anickel or nickel alloy layer 456. Each of the first ENEPET stack 420,the second ENEPET stack 430, the third ENEPET stack 440, and the fourthENEPET stack 450 may be formed using one of the methods described inFIGS. 1-3(A-D). Although the first ENEPET stack 420, second ENEPET stack430, the third ENEPET stack 440, and the fourth ENEPET stack 450 areeach depicted with the layers 424, 426, 434, 436, 444, 446, 454, and 456extending only along the base of the respective trench 433, 443, and443, as previously described with reference to FIG. 3A-D, the layers424, 426, 434, 436, 444, 446, 454, and 456 may also extend up sidewalkof the respective trench 423, 433, 443, and 453. The pitch between thefirst ENEPET stack 420 and the second ENEPET stack 430 may have adifferent X pitch than the Y pitch between the third ENEPET stack 440and the fourth ENEPET stack 450. In some examples, the X pitch and/orthe Y pitch may be 20-25 μm. In some examples, the X pitch may begreater than 100 μm and the Y pitch may be less than 25 μm. The firstENEPET stack 420, second ENEPET stack 430, the third ENEPET stack 440,and the fourth ENEPET stack 450 may connect to an aligned contact 460,contact 470, contact 480, and contact 490 of the die 404.

The first ENEPET stack 420 may connect to an electrode 428 that extendsdown through the ABF films 414 and 416. The second ENEPET stack 430 mayconnect to an electrode 438 that extends down through the ABF films 414and 416. The third ENEPET stack 440 and the fourth ENEPET stack 450 mayconnect to an electrode 448 and an electrode 458, respectively, thateach extend down through the ABF film 414 to an embedded multi-dieinterconnect bridge (EMIB) 418. The electrodes 428, 438, 448, and 458may each include a conductive material, such as copper or a copperalloy. The EMIB 418 may provide a high bandwidth connection between thedie 404 and another die (not shown). The EMIB 418 may be held in placeby a die-bond film (DBF) 419. By forming the first ENEPET stack 420, thesecond ENEPET stack 430, the third ENEPET stack 440, and the fourthENEPET stack 450 with an electroless deposition process using one of themethods described in FIGS. 1-3(A-D), variable pitch can be achieved inthe same package which may not be possible using traditional stenciltechnologies. Much finer pitches are possible compared to stencil-basedtechnologies

While the tin/tin alloy material 422, 432, 442, and 452 depicted in FIG.4 has a rectangular shape above the SR layer 412, it would beappreciated that the tin/tin alloy material 422, 432, 442, and 452 mayeach have a rounded circular or elliptical shape above the SR layer 412after a reflow and deflux process.

FIG. 5 illustrates a method 500 for forming a solder bump in accordancewith some embodiments. The method 500 may be implemented for thepackages 100-103 of FIGS. 1A-1D, respectively, the packages 200-203 ofFIGS. 2A-2D, respectively, the packages 300-303 of FIGS. 3A-3D,respectively, respectively, the 4 apparatus 400 of FIG. 4, orcombinations thereof.

In some embodiments, the method 500 may include forming an electrode inthe solder resist layer. In some embodiments, the method 500 may furtherinclude forming the trench in a solder resist layer of a package.

The method 500 may include forming a layer of a second material over afirst material at a base of a trench in the solder resist layer, at 510.The first material may include nickel or a nickel alloy and the secondmaterial may include palladium. In some examples, the method 500 mayfurther include forming a layer of the first material along the base ofthe trench in the solder resist layer. The first material may includethe first material 110 of FIGS. 1A-1D, the first material 210 of FIGS.2A-2D, the first material 310 of FIGS. 3A-3D, the layers 424, 434, 444,and/or 454 of FIG. 4, or combinations thereof. The second material mayinclude the second material 112 of FIGS. 1B-1D, the second material 212of FIGS. 2A-2D, the second material 312 of FIGS. 3B-3D, the layers 426,436, 446, and/or 456 of FIG. 4, or combinations thereof. The solderresist layer may include the solder resist layer 104 of FIGS. 1A-1D, thesolder resist layer 204 of FIGS. 2A-2D, the solder resist layer 304 ofFIGS. 3A-3D the solder resist layer 412 of FIG. 4, or combinationsthereof. The trench may include the trench 108 of FIGS. 1A-1B, thetrench 208 of FIG. 2A, the trench 308 of FIGS. 3A-3B, the trenches 423,433, 443, and/or 453 of FIG. 4, or combinations thereof.

In some examples, the method 500 may further include etching the solderresist layer to reduce the height of the solder resist layer prior toreflow and deflux of the solder bump. In some examples, the firstmaterial may contact an electrode, such as the electrode 110 of FIGS.1A-1D, the electrode 210 of FIGS. 2A-2D, the electrode 310 of FIGS.3A-3D the electrodes 428, 438, 448, and/or 458 of FIG. 4, orcombinations thereof. In some embodiments, forming the layer of thefirst material along the base of the trench in the solder resist layermay include forming a layer of the first material along sidewalls of thetrench in the solder resist layer. In some embodiments, forming thelayer of the second material may include forming a layer of the secondmaterial over the first material along sidewalls of the trench in thesolder resist layer

The method 500 may further include depositing a third material thatincludes tin or tin alloy on the second material using an electrolessdeposition process, at 520. The third material may include the thirdmaterial 120 of FIG. 1C, the third material 220 of FIGS. 2B-2C, thethird material 320 of FIG. 3C, the tin/tin alloy material 432, 442,and/or 452 of FIG. 4, or combinations thereof. In some embodiments, themethod 500 may further include, after depositing the third material,etching the solder resist layer to reduce a height of the solder resistlayer. In some examples, depositing the third material that includestin/tin alloy on the second material may include filling the trench withthe third material such that the third material extends to a top edge ofthe trench. In other examples, depositing the third material thatincludes tin/tin alloy on the second material may include filling thetrench with the third material such that the third material extendsabove a top edge of the trench.

The method 500 may further include forming a solder bump out of thethird material using a reflow and deflux process, at 530. The solderbump may include the solder bump 121 of FIG. 1D, the solder bump 221 ofFIG. 2D, the solder bump 321 of FIG. 3D, the tin/tin alloy material 422,432, 442, and/or 452 of FIG. 4, or combinations thereof. The solder bumpmay provide a connection point to connect to a connection point ofanother die, such as the die 404 of FIG. 4.

FIG. 7 illustrates a method 700 for forming multiple solder bump inaccordance with some embodiments. The method 700 may be implemented thepackages 100-103 of FIGS. 1A-1D, respectively, the packages 200-203 ofFIGS. 2A-2D, respectively, the packages 300-303 of FIGS. 3 A-3D,respectively, respectively, the apparatus 400 of FIG. 4, or combinationsthereof.

The method 600 may include forming a first pair of ENEPET stacks in asolder resist layer of a package, at 610. The first pair of ENEPETstacks may each may include the materials 110, 112, and 120/121 of FIGS.1C-1D, the materials 210, 212, and 220/221 of FIGS. 2B-2D, the materials310, 312, and 320/321 of FIGS. 3B-3D, the pair of the ENEPET stacks 420and 430 of FIG. 4, or combinations thereof.

In some examples, forming the first pair of ENEPET stacks in the solderresist layer of the package may include forming a layer of a secondmaterial over a first material at a base of a trench in the solderresist layer, and depositing a third material that includes tin/tinalloy on the second material using an electroless deposition process.The first material may include nickel or a nickel alloy and the secondmaterial may include palladium. In some examples, the second materialmay not include nickel. In some examples, the method 600 may furtherinclude forming a layer of the second material over the first materialalong sidewalls of the trench in the solder resist layer. The firstmaterial may include the first material 110 of FIGS. 1A-1D, the firstmaterial 210 of FIGS. 2A-2D, the first material 310 of FIGS. 3A-3D, thelayers 424, 434, 444, and/or 454 of FIG. 4, or combinations thereof. Thesecond material may include the second material 112 of FIGS. 1B-1D, thesecond material 212 of FIGS. 2A-2D, the second material 312 of FIGS.3B-3D, the layers 426, 436, 446, and/or 456 of FIG. 4, or combinationsthereof. The solder resist layer may include the solder resist layer 104of FIGS. 1A-1D, the solder resist layer 204 of FIGS. 2A-2D, the solderresist layer 304 of FIGS. 3A-3D, the solder resist layer 412 of FIG. 4,or combinations thereof. The trench may include the trench 108 of FIGS.1A-1B, the trench 208 of FIG. 2A, the trench 308 of FIGS. 3A-3B, thetrenches 423, 433, 443, and/or 453 of FIG. 4, or combinations thereof.The third material may include the third material 120 of FIG. 1C, thethird material 220 of FIGS. 2B-2C, the third material 320 of FIG. 3C,the tin/tin alloy material 422, 532, 442, and/or 452 of FIG. 4, orcombinations thereof.

The method 600 may further include, contemporaneously with forming thefirst pair of ENEPET stacks in the solder resist layer of the package,forming a second pair of ENEPET stacks in the solder resist layer of thepackage, at 620. A width of the first pair of ENEPET stacks may have agreater pitch than the second pair of ENEPET stacks. In some examples, apitch of the second pair of ENEPET stacks may be 20-25 μm. The secondpair of ENEPET stacks may include the materials 110, 112, and 120/121 ofFIGS. 1C-1D, the materials 210, 212, and 220/221 of FIGS. 2B-2D, thematerials 310, 312, and 320/321 of FIGS. 3B-3D, the pair of the ENEPETstacks 440 and or 450 of FIG. 4, or combinations thereof.

In some examples, the method 600 may further include forming a firstelectrode that extends through the solder resist layer, a firstAjinomoto build-up film (ABF) layer to a second ABF layer (e.g., theelectrode 428 or 438 of FIG. 4), and forming a second electrode thatextends through the solder resist layer and the first Ajinomoto build-upfilm to an interconnect bridge (e.g., the electrode 448 or 458 of FIG.4). The Ajinomoto build-up film may include the first ABF 514 of FIG. 4and the interconnect bridge may include the EMIB 418 of FIG. 4.

The first pair of ENEPET stacks and the second pair of ENEPET stacks maybe used as connection points to contacts of another die, such ascontacts 460, 470, 480, and 490 of the die 404 of FIG. 4.

To better illustrate the methods and device disclosed herein, anon-limiting list of embodiments is provided here:

Example 1 includes subject matter (such as a device, apparatus, ormachine) including a package comprising: a package comprising: solderresist layer; an electrode embedded in a bottom portion of the solderresist layer; and a solder bump extending through the solder resistlayer to the electrode, the solder bump including an electroless nickel,electroless palladium, electroless tin (ENEPET) stack.

In Example 2, the subject matter of Example 1 may include, wherein theENEPET stack comprises: a first layer contacting the electrode, whereinthe first layer includes a nickel-material; a second layer over thefirst layer, wherein the second layer includes palladium; and a thirdlayer over the second layer, wherein the third layer includes tin or atin alloy.

In Example 3, the subject matter of any one of Examples 1 to 2 mayinclude, wherein the package further comprises: a second electrodeembedded in a bottom portion of the solder resist layer in parallel withthe electrode; and a second solder bump extending through the solderresist layer to the second electrode, the second solder bump including asecond ENEPET stack; wherein a pitch between the second ENEPET stack andan adjacent stack is different than a pitch between the ENEPET stack anadjacent stack.

In Example 4, the subject matter of any one of Examples 1 to 3 mayinclude, wherein the pitch between the ENEPET stack the adjacent stackis less than 25 μm.

Example 5 includes subject matter (such as a device, apparatus, ormachine) comprising: a first pair of electroless nickel, electrolesspalladium, electroless tin (ENEPET) stacks formed in a solder resistlayer of the package having a first pitch; and a second pair of ENEPETstacks formed in the solder resist layer of the package having a secondpitch, wherein the first pitch is greater than the second pitch.

In Example 6, the subject matter of Example 5 may include, wherein thefirst pitch is greater than 100 μm and the second pitch is less than 25μm.

In Example 7, the subject matter of any one of Examples 5 to 6 mayinclude, wherein a first ENEPET stack of the first pair of ENEPET stacksin the solder resist layer of the package comprises: a layer of a firstmaterial at a base of a trench in the solder resist layer; a layer of asecond material over a first material at the base of the trench; and athird material that includes tin deposited on the second material usingan electroless deposition process.

In Example 8, the subject matter of any one of Examples 5 to 7 mayinclude, wherein the layer of the first material extends along thesidewalk of the trench in the solder resist layer, and where the layerof the second material extends over the first material along thesidewalls of the trench in the solder resist layer.

In Example 9, the subject matter of any one of Examples 5 to 8 mayinclude, wherein the first material includes nickel and the secondmaterial includes palladium.

In Example 10, the subject matter of any one of Examples 5 to 9 mayinclude, an first electrode that extends through a portion of the solderresist layer and through a first Ajinomoto build-up film (ABF) layer toa second ABF layer, wherein a first ENEPET stack of the pair of ENEPETstacks contacts the first electrode; and a second electrode that extendsthrough a portion of the solder resist layer and through the first ABFlayer to an interconnect bridge, wherein a second ENEPET stack of thepair of ENEPET stacks contacts the second electrode.

Example 11 includes subject matter (such as a method, means forperforming acts, machine readable medium including instructions thatwhen performed by a machine cause the machine to performs acts, or anapparatus to perform) to form a solder bump comprising: forming a layerof a second material over a first material at a base of a trench in asolder resist layer, wherein the first material includes nickel and thesecond material includes palladium; depositing a third material thatincludes tin on the second material using an electroless depositionprocess; and forming a solder bump out of the third material using areflow and deflux process.

In Example 12, the subject matter of Example 11 may include, forming alayer of the first material along the base of the trench in the solderresist layer.

In Example 13, the subject matter of any one of Examples 11 to 12 mayinclude, wherein the first material contacts an electrode.

In Example 14, the subject matter of any one of Examples 11 to 13 mayinclude, forming the electrode; and forming the solder resist layer overthe electrode.

In Example 15, the subject matter of any one of Examples 11 to 14 mayinclude, wherein forming the layer of the first material along the baseof the trench in the solder resist layer includes forming a layer of thefirst material along sidewalls of the trench in the solder resist layer.

In Example 16, the subject matter of any one of Examples 11 to 15 mayinclude, wherein forming the layer of the second material furthercomprises forming a layer of the second material over the first materialalong sidewalk of the trench in the solder resist layer.

In Example 17, the subject matter of any one of Examples 11 to 16 mayinclude, prior to forming the trench in the solder resist layer, etchingthe solder resist layer to reduce a height of the solder resist layer.

In Example 18, the subject matter of any one of Examples 11 to 17 mayinclude, after depositing the third material, etching the solder resistlayer to reduce a height of the solder resist layer.

In Example 19, the subject matter of any one of Examples 11 to 18 mayinclude, forming the trench in the solder resist layer.

In Example 20, the subject matter of any one of Examples 11 to 19 mayinclude, wherein the solder bump has a circular or elliptical shape.

In Example 21, the subject matter of any one of Examples 11 to 20 mayinclude, wherein depositing the third material that includes tin on thesecond material comprises filling the trench with the third materialsuch that the third material extends to a top edge of the trench.

In Example 22, the subject matter of any one of Examples 11 to 21 mayinclude, wherein depositing the third material that includes tin on thesecond material comprises filling the trench with the third materialsuch that the third material extends above a top edge of the trench.

Example 23 includes an apparatus comprising means for performing any ofthe Examples 10-22.

Example 24 includes subject matter (such as a method, means forperforming acts, machine readable medium including instructions thatwhen performed by a machine cause the machine to performs acts, or anapparatus to perform) to form a solder bump comprising: forming a firstpair of electroless nickel, electroless palladium, electroless tin(ENEPET) stacks in a solder resist layer of a package; andcontemporaneously with forming the first pair of ENEPET stacks in thesolder resist layer of the package, forming a second pair of ENEPETstacks in the solder resist layer of the package, wherein a pitchbetween the first pair of ENEPET stacks is greater than a pitch betweenthe second pair of ENEPET stacks.

In Example 25, the subject matter of Example 24 may include, wherein apitch of the second pair of ENEPET stack is less than 25 μm.

In Example 26, the subject matter of any one of Examples 24 to 25 mayinclude, wherein forming the first pair of ENEPET stacks in the solderresist layer of the package comprises: forming a layer of a secondmaterial over a first material at a base of a trench in the solderresist layer, wherein the first material includes palladium and nickeland the second material includes palladium; and depositing a thirdmaterial that includes tin on the second material using an electrolessdeposition process.

In Example 27, the subject matter of any one of Examples 24 to 26 mayinclude, forming a layer of the second material over the first materialalong sidewalls of the trench in the solder resist layer.

In Example 28, the subject matter of any one of Examples 24 to 27 mayinclude, forming a first electrode that extends through a portion of thesolder resist layer and through a first Ajinomoto build-up film (ABF)layer to a second ABF layer; and forming a second electrode that extendsthrough a portion of the solder resist layer and through the first ABFto an interconnect bridge.

Example 29 includes an apparatus comprising means for performing any ofthe Examples 24-28.

These examples are intended to provide non-limiting examples of thepresent subject matter—they are not intended to provide an exclusive orexhaustive explanation. The detailed description above is included toprovide further information about the present devices, and methods.

The above detailed description includes references to the accompanyingdrawings, which form a part of the detailed description. The drawingsshow, by way of illustration, specific embodiments in which thedisclosure can be practiced. These embodiments are also referred toherein as “examples.” Such examples can include elements in addition tothose shown or described. However, the present inventors alsocontemplate examples in which only those elements shown or described areprovided. Moreover, the present inventors also contemplate examplesusing any combination or permutation of those elements shown ordescribed (or one or more aspects thereof), either with respect to aparticular example (or one or more aspects thereof), or with respect toother examples (or one or more aspects thereof) shown or describedherein.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B,” “B but not A,” and “A and B,” unlessotherwise indicated. In this document, the terms “including” and “inwhich” are used as the plain-English equivalents of the respective terms“comprising” and “wherein.” Also, in the following claims, the terms“including” and “comprising” are open-ended, that is, a system, device,article, composition, formulation, or process that includes elements inaddition to those listed after such a term in a claim are still deemedto fall within the scope of that claim. Moreover, in the followingclaims, the terms “first,” “second,” and “third,” etc. are used merelyas labels, and are not intended to impose numerical requirements ontheir objects.

The above description is intended to be illustrative, and notrestrictive. For example, the above-described examples (or one or moreaspects thereof) may be used in combination with each other. Otherembodiments can be used, such as by one of ordinary skill in the artupon reviewing the above description. The Abstract is provided to complywith 37 C.F.R. §1.72(b), to allow the reader to quickly ascertain thenature of the technical disclosure. It is submitted with theunderstanding that it will not be used to interpret or limit the scopeor meaning of the claims. Also, in the above Detailed Description,various features may be grouped together to streamline the disclosure.This should not be interpreted as intending that an unclaimed disclosedfeature is essential to any claim. Rather, inventive subject matter maylie in less than all features of a particular disclosed embodiment.Thus, the following claims are hereby incorporated into the DetailedDescription, with each claim standing on its own as a separateembodiment, and it is contemplated that such embodiments can be combinedwith each other in various combinations or permutations. The scope ofthe disclosure should be determined with reference to the appendedclaims, along with the full scope of equivalents to which such claimsare entitled.

1. An apparatus including a package comprising: the package comprising:solder resist layer; an electrode embedded in a bottom portion of thesolder resist layer; and a solder bump extending through the solderresist layer to the electrode, the solder bump including an electrolessnickel, electroless palladium, electroless tin (ENEPET) stack.
 2. Theapparatus of claim 1, wherein the ENEPET stack comprises: a first layercontacting the electrode, wherein the first layer includes anickel-material; a second layer over the first layer, wherein the secondlayer includes palladium; and a third layer over the second layer,wherein the third layer includes tin or a tin alloy.
 3. The apparatus ofclaim 1, wherein the package further comprises: a second electrodeembedded in a bottom portion of the solder resist layer in parallel withthe electrode; and a second solder bump extending through the solderresist layer to the second electrode, the second solder bump including asecond ENEPET stack; wherein a pitch between the second ENEPET stack andan adjacent stack is different than a pitch between the ENEPET stack andan adjacent stack.
 4. The apparatus of claim 3, wherein the pitchbetween the ENEPET stack and the adjacent stack is less than 25 μm. 5.An apparatus including a package comprising: a first pair of electrolessnickel, electroless palladium, electroless tin (ENEPET) stacks formed ina solder resist layer of the package having a first pitch; and a secondpair of ENEPET stacks formed in the solder resist layer of the packagehaving a second pitch, wherein the first pitch is greater than thesecond pitch,
 6. The apparatus of claim 5, wherein the first pitch isgreater than 100 μm and the second pitch is less than 25 μm.
 7. Theapparatus of claims, wherein a first ENEPET stack of the first pair ofENEPET stacks in the solder resist layer of the package comprises: theelectroless nickel at a base of a trench in the solder resist layer; theelectroless palladium over the electroless nickel; and the electrolesstin deposited on the electroless palladium.
 8. The apparatus of claim 7,wherein the layer of the electroless nickel extends along the sidewallsof the trench in the solder resist layer, and where the layer of theelectroless palladium extends over the electroless nickel along thesidewalls of the trench in the solder resist layer.
 9. (canceled) 10.The apparatus of claim 5, further comprising: a first electrode thatextends through a portion of the solder resist layer and through a firstAjinomoto build-up film (ABF) layer to a second ABF layer, wherein afirst ENEPET stack of the first pair of ENEPET stacks contacts the firstelectrode; and a second electrode that extends through a portion of thesolder resist layer and through the first ABF layer to an interconnectbridge, wherein a second. ENEPET stack of the second pair of ENEPETstacks contacts the second electrode.
 11. A method to form a solder bumpcomprising: forming a layer of a second material over a first materialat a base of a trench in a solder resist layer, wherein the firstmaterial includes nickel and the second material includes palladium;depositing a third material that includes tin on the second materialusing an electroless deposition process; and forming a solder bump outof the third material using a reflow and deflux process.
 12. The methodof claim 11, further comprising forming a layer of the first materialalong the base of the trench in the solder resist layer.
 13. The methodof claim 12, wherein the first material contacts an electrode.
 14. Themethod of claim 13, further comprising: forming the electrode; andforming the solder resist layer over the electrode.
 15. The method ofclaim 12, wherein forming the layer of the first material along the baseof the trench in the solder resist layer includes forming a layer of thefirst material along sidewalls of the trench in the solder resist layer.16. The method of claim 11, wherein forming the layer of the secondmaterial further comprises forming a layer of the second material overthe first material along sidewalls of the trench in the solder resistlayer.
 17. The method of claim 11, further comprising, prior to formingthe trench in the solder resist layer, etching the solder resist layerto reduce a height of the solder resist layer.
 18. The method of claim11, further comprising forming the trench in the solder resist layer.19. The method of claim 11, wherein depositing the third material thatincludes tin on the second material comprises filling the trench withthe third material such that the third material extends to a top edge ofthe trench.
 20. The method of claim 11, wherein depositing the thirdmaterial that includes tin on the second material comprises filling thetrench with the third material such that the third material extendsabove a top edge of the trench.
 21. A method to form a solder bumpcomprising: forming a first pair of electroless nickel, electrolesspalladium, electroless tin (ENEPET) stacks in a solder resist layer of apackage; and contemporaneously with forming the first pair of ENEPETstacks in the solder resist layer of the package, forming a second pairof ENEPET stacks in the solder resist layer of the package, wherein apitch between the first pair of ENEPET stacks is greater than a pitchbetween the second pair of ENEPET stacks.
 22. The method claim 21,wherein a pitch of the second pair of ENEPET stack is less than 25 μm.23. The method of claim 21, wherein forming the first pair of ENEPETstacks in the solder resist layer of the package comprises: forming alayer of a second material over a first material at a base of a trenchin the solder resist layer, wherein the first material includespalladium and nickel and the second material includes palladium; anddepositing a third material that includes tin on the second materialusing an electroless deposition process.
 24. The method of claim 23,further comprising forming a layer of the second material over the firstmaterial along sidewalls of the trench in the solder resist layer. 25.The method of claim 21, further comprising: forming a first electrodethat extends through a portion of the solder resist layer and through afirst Ajinomoto build-up film (ABF) layer to a second ABF layer; andforming a second electrode that extends through a portion of the solderresist layer and through the first ABF to an interconnect bridge.